Method of treating metals using ureido silanes and multi-silyl-functional silanes in admixture

Abstract

The present invention relates to a method of metal treatment, particularly a method of metal treatment in order to improve corrosion resistance. The method comprises applying a solution containing one or more ureido silanes in admixture with one or more multi-silyl-functional; silanes to a metal substrate. The method is particularly suitable for use on cold-rolled steel, zinc, iron, aluminium and aluminium alloy surfaces.

What is claimed is: 
     
       1. A method of treating a metal sheet, comprising the steps of: (a) providing a metal substrate, the said metal substrate chosen from the group consisting of: cold-rolled steel   steel coated with a metal chosen from the group consisting of: zinc, zinc alloy, aluminum and aluminum alloy;   iron;   aluminum; and   aluminum alloy; and     (b) applying a coating on the metal substrate by contacting the metal substrate with a solution containing one or more hydrolyzed or partially hydrolyzed ureido silanes, one or more hydrolyzed or partially hydrolyzed multi-silyl-functional silanes and a solvent, wherein the ratio of multi-silyl-functional silanes to ureido silanes in the solution is in the range of 1:1-1:10, and   substantially removing the solvent.   
     
     
       2. The method according to claim 1, further comprising the step of curing said coating after step (b) at a temperature of between about 40° C. and 180° C. 
     
     
       3. The method according to claim 1, further comprising the step of applying a second solution containing one or more hydrolyzed or partially hydrolyzed ureido silanes and one or more hydrolyzed or partially hydrolyzed multi-silyl-functional silanes to said metal substrate. 
     
     
       4. The method according to claim 1, further comprising the step of applying a second solution containing one or more hydrolyzed or partially hydrolyzed organofunctional silanes. 
     
     
       5. The method according to claim 1, wherein the multi-silyl-functional silane has the general structure ##STR5## wherein Z is selected from the group consisting of C 1  -C 6  alkylene, C 1  -C 6  alkenylene, C 1  -C 6  alkylene substituted with at least one amino group, C 1  -C 6  alkenylene substituted with at least one amino group, arlyene and alkylarylene and R 3  is selected from the group consisting of hydrogen, C 1  -C 24  alkyl and C 2  -C 24  acyl, and may be the same or different; and, n is 2 or 3, and further wherein Z may be a bond when n is 2.   
     
     
       6. The method according to claim 5, wherein R 3  is selected from the group consisting of hydrogen, C 1  -C 6  alkyl and C 2  -C 4  acyl, and may be the same or different. 
     
     
       7. The method according to claim 6, wherein each R 3  is individually chosen from the group consisting of: ethyl, methyl, propyl, iso-propyl, butyl, iso-butyl, sec-butyl, tert-butyl and acetyl. 
     
     
       8. The method of claim 1, wherein said ureido silane is substantially γ-ureidopropyltriethoxysilane. 
     
     
       9. The method of claim 1, wherein the multi-silyl-functional silane is 1,2-bis-(triethoxysilyl)ethane. 
     
     
       10. The method according claim 1, wherein the solution additionally comprises an acid. 
     
     
       11. The method according to claim 10, wherein the acid is selected from the group consisting of acetic, oxalic, formic or propionic acid. 
     
     
       12. The method according to according to claim 1, wherein the solvent comprises an organic solvent. 
     
     
       13. The method according to claim 12, wherein the solvent is an alcohol. 
     
     
       14. The method according to claim 1, wherein the solvent comprises water. 
     
     
       15. The method of claim 1, wherein a polymer coating is applied on top of the silane coating. 
     
     
       16. The method of claim 15, wherein the polymer coating is selected from the group consisting of paint, rubber and adhesive. 
     
     
       17. The method of claim 1, wherein the concentration of multi-silyl-functional silanes in the solution is between about 0.1% and about 10%. 
     
     
       18. The method of claim 1, wherein the concentration of ureido silanes in the solution is between about 0.1 and 10%. 
     
     
       19. The method of claim 1, wherein the ratio of multi-silyl-functional silanes to ureido silanes is in the range of 1:1:-1:8. 
     
     
       20. A method of permanently improving the corrosion resistance of a metal sheet, comprising the steps of: (a) providing a metal substrate, the said metal substrate chosen from the group consisting of: cold-rolled steel   steel coated with a metal chosen from the group consisting of: zinc, zinc alloy, aluminum and aluminum alloy;   iron;   aluminum; and   aluminum alloy; and     (b) applying a solution to the metal substrate containing one or more hydrolyzed or partially hydrolyzed ureido silanes, one or more hydrolyzed or partially hydrolyzed multi-silyl-functional silanes and a solvent wherein the ratio of multi-silyl-functional silanes to ureido silanes in the solution is in the range of 1:1-1:10.   
     
     
       21. The method of claim 1 wherein the concentration of multi-silyl-functional silanes is between about 0.2% and about 2%. 
     
     
       22. The method of claim 1 wherein the concentration of multi-silyl-functional silanes is about 0.5%. 
     
     
       23. The method of claim 1 wherein the concentration of ureido silanes in the solution is between about 0.2% and about 3%. 
     
     
       24. The method of claim 1 wherein the concentration of ureido silanes in the solution is about 2%. 
     
     
       25. The method of claim 1 wherein the ratio of multi-silyl-functional silanes to ureido silanes is 1:4. 
     
     
       26. The method of claim 1, wherein the step of applying said coating on the metal substrate comprises dipping the metal substrate into the solution so that the metal substrate contacts the solution for a period of time between about 1 second and about 20 minutes. 
     
     
       27. The method of claim 26 wherein the metal substrate contacts the solution for a period of time between about 10 seconds and 2 minutes. 
     
     
       28. The method according to claim 1, wherein the ureido silanes have the general structure ##STR6## where R is chosen from the group consisting of hydrogen, C 1  -C 24  alkyl, and C 2  -C 24  acyl wherein each R may be the same or different; X is selected from the group consisting of a bond, C 1  -C 6  alkylene, C 1  -C 6  alkenylene, C 1  -C 6  alkylene substituted with at least one amino group, C 1  -C 6  alkenylene substituted with at least one amino group, arylene and alkylarylene; and, R 1  and R 2  are groups individually selected from the group consisting of hydrogen, C 1  -C 6  alkyl, C 2  -C 6  alkenyl, C 1  -C 6  alkyl substituted with at least one amino group, C 1  -C 6  alkenyl substituted with at least one amino group, arylene and alkylarylene. 
     
     
       29. The method according to claim 28, wherein each R is individually chosen from the group consisting of hydrogen, ethyl, methyl, propyl, iso-propyl, butyl, iso-butyl, sec-butyl, tert-butyl and acetyl, wherein each R may be the same or different. 
     
     
       30. The method according to claim 28, wherein R 1  and R 2  are individually selected from the group consisting of hydrogen, ethyl, methyl, propyl, iso-propyl, butyl, iso-butyl, sec-butyl, tert-butyl and acetyl.